1. Field of the Invention
This invention relates to a transmission case housing a transmission mechanism for transmitting power to dirigible wheels of a relatively small working vehicle such as a lawn mower, agricultural tractor or rice planter.
2. Description of the Related Art
Generally, the transmission case noted above includes an axle case having a main body and vertical bosses extending in a bent way from opposite ends of the main body, and pivoting cases supporting axles of the dirigible wheels. In the case of a tractor, as disclosed in Japanese Unexamined Patent Publication H10-250391, and in the case of a riding rice planter, as disclosed in Japanese Unexamined Patent Publication H7-17203, the pivoting cases supporting the axles of dirigible front wheels are attached to the vertical bosses at the right and left ends of the axle case to be pivotable about vertical axes. Power is transmitted from a cross transmission shaft extending through the axle case to the axles in the pivoting cases through vertical transmission shafts extending along the vertical axes.
In the conventional construction noted above, the main body and the vertical bosses of the axle case are separate components interconnected through flanges to allow assembly into the case of transmission shafts and bevel gears. However, the main body of the axle case is formed as a linear tube, and the vertical bosses are formed as short tubes bent at approximately right angles (in the shape of elbows). The components assembled into these tubular members are subject to restrictions as to outside diameter and assembled position. This leads to a disadvantage of requiring an excessively large inside diameter of the transmission case.